1. Field of the Invention
The present general inventive concept relates to a method of manufacturing an inkjet printhead and an inkjet printhead manufactured using the method, and more particularly, to a method of manufacturing an inkjet printhead in which a shape of an ink ejection nozzle can be controlled.
2. Description of the Related Art
An inkjet printhead is an apparatus that ejects ink droplets on desired positions of a recording paper in order to print predetermined color images. Inkjet printheads are categorized into two types according to the ink droplet ejection mechanism used: a thermal inkjet printhead and a piezoelectric inkjet printhead. The thermal inkjet printhead ejects ink droplets due to an expansion force of ink bubbles generated by thermal energy. The piezoelectric inkjet printhead ejects ink droplets by pressure applied to ink due to a deformation of a piezoelectric body. The two types of inkjet printheads use a different operating element, but each push ink droplets with a predetermined energy.
FIG. 1 illustrates a conventional thermal inkjet printhead. Referring to FIG. 1, the conventional inkjet printhead includes a substrate 10, a flow path forming layer 20 stacked on the substrate 10, and a nozzle layer 30 formed on the flow path forming layer 20. An ink feed hole 51 is formed in the substrate 10. An ink chamber 53 in which ink is filled and a restrictor 52 that connects the ink feed hole 51 and the ink chamber 53 are formed in the flow path forming layer 20. A nozzle 54 through which the ink is ejected from the ink chamber 53 is formed in the nozzle layer 30. In addition, a heater 41, made of a heating resistor to heat the ink in the ink chamber 53, and an electrode 42, to apply a current to the heater 41, are formed on the substrate 20.
The ink droplet ejection mechanism of the thermal inkjet printhead is as follows. Ink is supplied from an ink storage container (not illustrated) to the ink chamber 53 through the ink feed hole 51 and the restrictor 52. The ink that is filled in the ink chamber 53 is heated by the heater 41. Accordingly, ink bubbles are generated by ink evaporation, and the generated bubbles are expanded to exert pressure on the ink filled in the ink chamber 53. Thereafter, ink droplets are ejected through the nozzle 54 out of the ink chamber 53.
When an ink droplet is ejected outside of the nozzle 54, a meniscus of the ink in the ink chamber 53 retreats to the restrictor 52, and ink is refilled up to the nozzle 54 by capillary action. In this case, particularly when the nozzle 54 is perpendicular to the substrate 10, a convex meniscus protrudes to an outside of the nozzle 54 by a pressure applied thereto, and thus there is a time delay before the meniscus returns to a concave form. Accordingly, high speed ink droplet ejection is difficult to achieve and sizes of the ink droplets are not uniform.
Accordingly, attempts have been made to solve the above problems by modifying a shape of a nozzle in various ways. It is known that when a nozzle is tapered, the tapering affects a behavior of an ink meniscus or a shape of ink ejection in various ways. For example, a capillary force of an ink meniscus becomes larger when a curvature of the meniscus is large as compared to when the curvature of the meniscus is small, and thus if the curvature of the meniscus of the ink that moves to the nozzle is reduced, the flux of the ink can be suppressed. Thus a nozzle may be tapered, having a diameter that decreases in an ejecting direction of ink therefrom. However, even when a nozzle is tapered, a flux of ink can vary depending on a viscosity of the ink. Thus it is difficult to obtain an appropriate tapered angle.
A nozzle can be tapered by processing a polyimide-based resin using an Excimer laser. However, it is difficult to obtain a sharply tapered nozzle using an Excimer laser and a cost thereof is high.
Alternatively, a nozzle can be tapered in a mold by fabricating a mold having a shape of a taper by heating a thermoplastic resin and filling the mold with a resist composition. However, a taper mold fabricated by heat does not demonstrating good reproducibility.
Also, a nozzle can be tapered stepwise by selectively radiating light, such as UV radiation, twice or more. However, this method is complicated and thus is not practical.